This invention relates generally to video inspection systems, and more specifically relates to a measurement system in a video inspection system.
There are numerous situations that arise while using a video inspection system, particularly a remote video inspection system, where there is a need to determine the size of a target object that appears within the video field. In the medical arena for example, when a doctor utilizes a video colposcope to inspect the vagina, cervix and/or uterus of a patient, it is important to be able to determine the size of certain objects within the video field. For instance, if a lesion/pathology appears in the video field, it is important to quantify the size of the object to determine the extent of the lesion/pathology and to determine if treatments are effective in reducing the lesion/pathology.
To date, determining the size of an object that appears in the video field has been accomplished through various means. One such method is described in U.S. Pat. No. 5,577,130 to Wu. Wu discloses a method and apparatus for determining the distance between an image and an object. The invention employs stereo vision methodology for determining depth information between an object and an image. The method involves displacing the imaging means (camera) and utilizes at least two of the successive images of an object that are generated. The relationship between the amount of displacement and the disparity in pixels in the successive images is used to mathematically determine the distance of an object from the video imaging means.
Another method is described in U.S. Pat. No. 5,070,401 to Salvati et al., which patent is owned by a common assignee of the present applicant. Salvati discloses a method of video measurement with automatic calibration and distortion correction. The method involves projecting a known supplementary image into the target area, counting the pixels associated with the known supplementary image, calibrating the system by using the known information, counting the pixels associated with the object of interest in the targets, and determining the physical characteristics of the object of interest.
Another method of determining the size of an object in a video field is described in U.S. Pat. No. 4,980,763 to Lia, which patent is owned by a common assignee of the present applicant. Lia discloses a system for measuring the size of objects viewed with a borescope. The patent discloses the use of a shadow generating means and image detecting means to detect the image of the object of interest and the contrasting shadow. The size of the object of interest can be calculated by measuring parameters of the contrasting image.
Yet another method is described in U.S. Pat. No. 4,115,804 to Morton et al. Morton discloses a method of image analysis for identifying measurement data from single and multiple fields of scan and for the control of feature measurement generation through the use of keyboard and visual displays. The invention is intended to overcome the effects of noise variability in obtaining alignment between points between different fields of scan and successful correlation of information obtained from successive fields of scan.
Another method is described in U.S. Pat. No. 3,730,632 to Chikama. Chikama discloses an object measurement system for an endoscope. The system projects an image of the target onto an image viewing surface. The image viewing surface comprises a scale indicating the length measurement. The scale is proportionately varied in relation to relative movement of an object lens assembly, said movement serving to focus the image of the object on the viewing surface.
The prior art contains methods of measurement that require at least two successive images in order to determine the measurement, which entails complex mathematical calculations and requires increased computer memory. The prior art also contains methods that an image of a supplementary object which is either integral to or projected into the video field. There is a need to provide a simpler apparatus and method of calculating the size of an object that appears in a video image. There is also the need to provide an apparatus and method of calculating the size of an object that appears in a video image that does not require relatively complex mathematical manipulations or the need for supplementary images within the video field.
It is therefore an object of the invention to provide an improved means of measuring an object through a video inspection system.
It is another object of the invention to provide an improved means of measuring an object through a video inspection system without the need to use successive images to determine the measurement.
It is yet another object of the invention to provide an improved means of measuring an object through a video inspection system without the need to provide a supplemental image within the video field.
These and other objects are accomplished by providing a measurement system comprising a lens system having selected optical characteristics and a CCD imager. The system includes a video display and an image overlay generator to select the target object in the video display. The image overlay generator allows the operator to mark the image and determines the number of pixels between cursor marks. The system includes a focusing mechanism including a focus motor with a servo feedback that provides focus data and a zoom mechanism including a zoom motor with a servo feedback that provides zoom data. The system includes a microprocessor/CPU that calculates the size of the target object by mathematically manipulating the optical characteristics, the focus data, the zoom data, and the pixel data.